netdev - Re: [PATCH 07/30] aio: add delayed cancel support

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Message-ID: <20180329180831.GA15948@lst.de>
Date:   Thu, 29 Mar 2018 20:08:31 +0200
From:   Christoph Hellwig <hch@....de>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     Christoph Hellwig <hch@....de>, Avi Kivity <avi@...lladb.com>,
        linux-aio@...ck.org, linux-fsdevel@...r.kernel.org,
        netdev@...r.kernel.org, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/30] aio: add delayed cancel support

On Thu, Mar 29, 2018 at 03:25:06PM +0100, Al Viro wrote:
> OK.  Let's leave that alone for now.  Re deferred cancels - AFAICS, we *must*
> remove the sucker from ctx->active_reqs before dropping ->ctx_lock.
> 
> As it is, you are creating a io_cancel()/io_cancel() race leading to double
> fput().  It's not that hard to fix; I can do that myself while applying your
> series (as described in previous posting - kiocb_cancel_locked() returning
> NULL or ERR_PTR() in non-deferred case and pointer to aio_kiocb removed from
> ->active_reqs in deferred one) or you could fix it in some other way and
> update your branch.

I think that is the right fix.  Let me resend so that I can test the
result first.